1. Field of the Invention
This invention relates to a high voltage power supply device for a vehicle such as, for example, a hybrid vehicle or an electric vehicle which are driven at least in part by an electric motor. Although not limited thereto, the invention has applicability to two-wheeled vehicles.
2. Description of the Related Art
Conventional electric automobiles run using an electric motor driven by electric power from batteries. Conventional hybrid vehicles in turn run using a combination of a gasoline engine and an electric motor. In such vehicles, a power supply battery device is required to supply high voltage for operating an electric motor so as to efficiently generate high output.
Regarding vehicles that use a high voltage power supply battery device, it is conventional to incorporate a safety plug unit that mechanically opens a high voltage circuit for inspection and maintenance.
For example, in Japanese publication no. JP 2004-007919, a removable safety plug is placed in the middle of a circuit connecting multiple batteries to each other in series. When the safety plug is removed from a battery container housing the batteries, the battery series circuit is mechanically disconnected.
Specifically, JP 2004-007919 discloses a power supply device in which twelve batteries each having 24V are connected to each other in series to generate voltage of 288V. A safety plug is placed in the middle of the series connection, i.e., at a connecting portion between the sixth battery and the seventh battery (a first embodiment). Also, a second embodiment suggests a structure in which plug electrodes are placed at three portions in the middle of a battery series circuit having 12 batteries, i.e., a safety plug structure in which plug electrodes are placed every three batteries.
However, the structure disclosed in JP 2004-007919 lacks safety. That is, even though the safety plug is removed from the battery containing box to disconnect the battery series circuit, voltage of 144V (i.e., 288/2) is still applied to an electrode section of the battery container into which the safety plug is inserted. Also, in the second embodiment, a voltage of 72V (i.e., 288/4) is applied to the electrode section. In general, resistance of a human body can be 3-5Ko, and a current amount that affects the human body can be 10 mA.
Accordingly, a voltage of 50V (0.01 A×5000o) can be a criterion for a safe voltage exposure for human beings. Therefore, a further reduction of the voltage is required than provided in the structure of JP 2004-007919.
Because the plug electrodes are inserted every three batteries of a battery line which is arranged in line in the second embodiment of JP 2004-007919 that has multiple safety plugs, intervals between three plug electrodes are inevitably large. If, the three plug electrodes need to be inserted simultaneously, the size of the safety plug itself would need to be increased.